Editing Conjunctivitis

{{short description| Inflammation of the eye}}
{{Redirect|Pinkeye|other uses|Pinkeye (disambiguation)}}
{{cs1 config|name-list-style=vanc|display-authors=6}}
{{Use dmy dates|date=January 2018}}
{{More citations needed|date=May 2024}}{{Infobox medical condition (new)
| name            = Conjunctivitis
| image           = An eye with viral conjunctivitis.jpg
| caption         = An eye with viral conjunctivitis
| field           = [[Ophthalmology]], [[optometry]]
| synonyms        = Pink eye
| symptoms        = [[Reddish eye]], scratchiness<ref name=NIH2015/>
| complications   =
| onset           =
| duration        = Viral conjunctivitis: up to two weeks<ref>{{Cite book | vauthors = Long SS, Prober CG, Fischer M |url=https://books.google.com/books?id=Xw7VDgAAQBAJ&pg=PA502 |title=Principles and Practice of Pediatric Infectious Diseases E-Book |date=2017 |publisher=Elsevier Health Sciences |isbn=978-0-323-46132-0 |page=502 |language=en}}</ref>
| causes          = [[viral infection|Viral]], [[bacterial infection|bacterial]], allergies<ref name=Az2013/>
| risks           =
| diagnosis       = Based on symptoms, [[microbial culture]]<ref name=NIH2015/>
| differential    =
| prevention      = [[Handwashing]]<ref name=NIH2015/>
| treatment       = Based on underlying cause<ref name=Az2013/>
| medication      =
| prognosis       =
| frequency       = 3–6 million per year (US)<ref name=NIH2015/><ref name=Az2013/>
| deaths          =
}}

'''Conjunctivitis''', also known as '''pink eye''' or '''Madras eye''',<ref>{{Cite web |title=What is Viral Conjunctivitis a.k.a. Sore Eyes? &#124; National Institutes of Health |url=http://nih.upm.edu.ph/health/what-viral-conjunctivitis-aka-sore-eyes}}</ref><ref>{{cite journal | vauthors = Mohanasundaram AS, Gurnani B, Kaur K, Manikkam R | title = Madras eye outbreak in India: Why should we foster a better understanding of acute conjunctivitis? | journal = Indian Journal of Ophthalmology | volume = 71 | issue = 5 | pages = 2298–2299 | date = May 2023 | pmid = 37202982 | pmc = 10391441 | doi = 10.4103/IJO.IJO_3317_22 | doi-access = free }}</ref> is [[inflammation]] of the [[conjunctiva]], the thin, clear layer that covers the white surface of the eye and the inner [[eyelid]].<ref name="Peads10">{{cite journal | vauthors = Richards A, Guzman-Cottrill JA | title = Conjunctivitis | journal = Pediatrics in Review | volume = 31 | issue = 5 | pages = 196–208 | date = May 2010 | pmid = 20435711 | doi = 10.1542/pir.31-5-196 | s2cid = 245084568 }}</ref> It makes the eye appear pink or reddish.<ref name=NIH2015/> Pain, burning, scratchiness, or itchiness may occur.<ref name=NIH2015/> The affected eye may have increased tears or be "stuck shut" in the morning.<ref name=NIH2015/> Swelling of the [[sclera]] may also occur.<ref name=NIH2015/> Itching is more common in cases due to allergies.<ref name=Az2013/> Conjunctivitis can affect one or both eyes.<ref name=NIH2015/> 

The most common infectious causes in adults are viral, whereas in children bacterial causes predominate.<ref name="Durand 2023">{{cite journal | vauthors = Durand ML, Barshak MB, Sobrin L | title = Eye Infections | journal = The New England Journal of Medicine | volume = 389 | issue = 25 | pages = 2363–2375 | date = December 2023 | pmid = 38118024 | doi = 10.1056/NEJMra2216081 | s2cid = 266433325 }}</ref><ref name="Az2013">{{cite journal | vauthors = Azari AA, Barney NP | title = Conjunctivitis: a systematic review of diagnosis and treatment | journal = JAMA | volume = 310 | issue = 16 | pages = 1721–1729 | date = October 2013 | pmid = 24150468 | pmc = 4049531 | doi = 10.1001/jama.2013.280318 }}</ref> The viral infection may occur along with other symptoms of a [[common cold]].<ref name=NIH2015/> Both viral and bacterial cases are easily spread between people.<ref name=NIH2015/> Allergies to pollen or animal hair are also a common cause.<ref name=Az2013/> Diagnosis is often based on signs and symptoms.<ref name=NIH2015/> Occasionally, a sample of the discharge is sent for [[microbial culture|culture]].<ref name=NIH2015/>

<!-- Prevention and treatment -->
Prevention is partly by [[handwashing]].<ref name=NIH2015/> Treatment depends on the underlying cause.<ref name="NIH2015">{{Cite web |date=November 2015 |title=Facts About Pink Eye |url=https://nei.nih.gov/health/pinkeye/pink_facts |url-status=live |archive-url=https://web.archive.org/web/20160309104846/https://nei.nih.gov/health/pinkeye/pink_facts |archive-date=9 March 2016 |access-date=8 March 2016 |website=National Eye Institute |df=dmy-all}}</ref> In the majority of viral cases, there is no specific treatment.<ref name=Az2013/> Most cases due to a bacterial infection also resolve without treatment; however, [[antibiotic]]s can shorten the illness.<ref name=NIH2015/><ref name=Az2013/> People who wear [[contact lenses]] and those whose infection is caused by [[gonorrhea]] or [[Chlamydia infection|chlamydia]] should be treated.<ref name=Az2013/> Allergic cases can be treated with [[antihistamine]]s or [[mast cell inhibitor]] drops.<ref name=Az2013/>

About 3 to 6 million people get acute conjunctivitis each year in the United States.<ref name=NIH2015/><ref name=Az2013/> Typically, people get better in one or two weeks.<ref name=NIH2015/><ref name=Az2013/> If visual loss, significant pain, sensitivity to light or signs of [[herpes]] occur, or if symptoms do not improve after a week, further diagnosis and treatment may be required.<ref name=Az2013/> Conjunctivitis in a newborn, known as [[neonatal conjunctivitis]], may also require specific treatment.<ref name=NIH2015/>
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== Signs and symptoms ==
[[File:Bloodshot eye.jpg|thumb|Bloodshot eyes]]

[[Red eye (medicine)|Red eye]], [[chemosis|swelling of the conjunctiva]], and [[epiphora (medical)|watering]] of the eyes are symptoms common to all forms of conjunctivitis. However, the pupils should be normally reactive, and the visual acuity normal.<ref>{{cite book | vauthors = Hashmi MF, Gurnani B, Benson S | chapter = Conjunctivitis |date=2023 | title = StatPearls | chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK541034/ |access-date=2023-05-23 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=31082078 }}</ref>

Conjunctivitis is identified by inflammation of the conjunctiva, manifested by irritation and redness. Examination using a [[slit lamp]] (biomicroscope) may improve diagnostic accuracy. Examination of the palpebral conjunctiva, that overlying the inner aspects of the eyelids, is usually more diagnostic than examination of the bulbal conjunctiva, that overlying the sclera.<ref>{{Cite web |date=2017-10-19 |title=Conjunctivitis |url=https://www.nhs.uk/conditions/conjunctivitis/ |access-date=2025-02-13 |website=nhs.uk |language=en}}</ref>

=== Viral ===
[[File:Conjunctivitis disease.jpg|thumb|Viral conjunctivitis]]
Approximately 80% of cases of conjunctivitis in adults and less than 20% in children are due to viruses, with 65% to 90% of these cases being attributed to adenoviruses.<ref name="Az2013"/><ref name="Durand 2023" />
Viral conjunctivitis is often associated with an infection of the upper respiratory tract, a common cold, or a sore throat. Other associated signs may include [[Preauricular deep parotid lymph nodes|pre-auricular]] lymph node swelling and contact with another person with a red eye.<ref name="Durand 2023" /> Eye pain may be present if the cornea is also involved.<ref name="Durand 2023" /> Its symptoms include excessive watering and itching. The discharge in viral conjunctivitis is usually (but not always) watery in nature.<ref name="Durand 2023" /> The infection usually begins in one eye but may spread easily to the other eye.{{citation needed|date=February 2023}}

Viral conjunctivitis manifests as a fine, diffuse pinkness of the conjunctiva which may be mistaken for [[iritis]], but corroborative signs on [[microscopy]], particularly numerous [[Lymph follicle|lymphoid follicle]]s on the [[Tarsus (eyelids)|tarsal]] conjunctiva, and sometimes a [[punctate keratitis]] are seen.{{citation needed|date=February 2023}}

=== Allergic ===
[[File:Allergicconjunctivitis.jpg|thumb|right|An eye with [[allergic conjunctivitis]] showing conjunctival edema]]
[[Allergic conjunctivitis]] is [[Allergic Inflammation|inflammation]] of the conjunctiva due to allergy.<ref name="Bielory">{{cite journal | vauthors = Bielory L, Friedlaender MH | title = Allergic conjunctivitis | journal = Immunology and Allergy Clinics of North America | volume = 28 | issue = 1 | pages = 43–58, vi | date = February 2008 | pmid = 18282545 | doi = 10.1016/j.iac.2007.12.005 | s2cid = 34371872 }}</ref> The specific [[allergen]]s may differ among patients. Symptoms result from the release of [[histamine]] and other active substances by [[mast cell]]s, and consist of redness (mainly due to [[vasodilation]] of the peripheral small blood vessels), swelling of the conjunctiva, itching, and increased production of tears.{{citation needed|date=September 2022}}

=== Bacterial ===

[[File:Swollen eye with conjunctivitis.jpg|thumb|right|An eye with bacterial conjunctivitis]]
Bacteria are responsible for approximately 70% of conjunctivitis in children and less than 20% of cases in adults.<ref name="Durand 2023" /> Common bacteria responsible for bacterial conjunctivitis are ''[[Staphylococcus]]'' including [[Staph aureus]], ''[[Streptococcus]]'' such as [[strep pneumoniae]],<ref>{{Cite web |title=Pink Eye (Conjunctivitis) |url=http://www.medicinenet.com/pink_eye/article.htm |url-status=live |archive-url=https://web.archive.org/web/20130622062209/http://www.medicinenet.com/pink_eye/article.htm |archive-date=22 June 2013 |publisher=MedicineNet |df=dmy-all}}</ref> ''[[Haemophilus]]'' species and [[Moraxella catarrhalis]].<ref name="Durand 2023" /> Less commonly, ''Chlamydia'' spp. and Niesseria species ([[Neisseria gonorrhoeae]] and [[Neisseria meningitidis]]) may be the cause.<ref name="Durand 2023" /><ref name="merck">{{Cite web |title=Acute Bacterial Conjunctivitis – Eye Disorders |url=http://www.merckmanuals.com/professional/eye-disorders/conjunctival-and-scleral-disorders/acute-bacterial-conjunctivitis |url-status=live |archive-url=https://web.archive.org/web/20161228184316/http://www.merckmanuals.com/professional/eye-disorders/conjunctival-and-scleral-disorders/acute-bacterial-conjunctivitis |archive-date=28 December 2016 |access-date=31 December 2016 |website=Merck Manuals Professional Edition |df=dmy-all}}</ref> Infection with ''[[Escherichia coli]]'' may also cause conjunctivitis, particularly in the [[Infant|neonatal]] subtype [[ophthalmia neonatorum]].<ref>{{cite journal | vauthors = Saadeh-Jackson S, Rodriguez L, Leffler CT, Freymiller C, Wolf E, Wijesooriya N, Couser NL | title = Ophthalmia neonatorum due to ''Escherichia coli'': A rare cause or an emerging bacterial etiology of neonatal conjunctivitis? | journal = Clinical Case Reports | volume = 10 | issue = 8 | pages = e6201 | date = August 2022 | pmid = 35949413 | pmc = 9354094 | doi = 10.1002/ccr3.6201 }}</ref> Bacterial conjunctivitis usually causes a rapid onset of conjunctival redness, swelling of the eyelid, and a sticky discharge. Typically, symptoms develop first in one eye, but may spread to the other eye within 2–5 days.  Conjunctivitis due to common [[pyogenic|pus-producing]] bacteria causes marked grittiness or irritation and a stringy, opaque, greyish or yellowish [[mucopurulent discharge|discharge]] that may cause the lids to stick together, especially after sleep.  Severe crusting of the infected eye and the surrounding skin may also occur.  The gritty or scratchy feeling is sometimes localized enough that patients may insist that they have a foreign body in the eye.{{citation needed|date=September 2022}}

[[File:Membranous conjunctivitis.jpg|thumb|right|Typical membranous conjunctivitis]]

Bacteria such as ''[[Chlamydia trachomatis]]'' or ''[[Moraxella]]'' spp. can cause a nonexudative but persistent conjunctivitis without much redness.  Bacterial conjunctivitis may cause the production of membranes or pseudomembranes that cover the conjunctiva.  Pseudomembranes consist of a combination of [[inflammatory cell]]s and exudates and adhere loosely to the conjunctiva, while true membranes are more tightly adherent and cannot be easily peeled away.  Cases of bacterial conjunctivitis that involve the production of membranes or pseudomembranes are associated with ''[[Neisseria gonorrhoeae]]'', β-hemolytic streptococci, and ''[[Corynebacterium diphtheriae]]''.  ''C. diphtheriae'' causes membrane formation in conjunctiva of unimmunized children.<ref>{{Cite book |title=Epidemiology and Prevention of Vaccine-Preventable Diseases |publisher=U.S. Dept. of Health & Human Services, Centers for Disease Control and Prevention |year=2015 |isbn=978-0-9904491-1-9 |veditors=Hamborsky J, Kroger A, Wolfe C |pages=112}}</ref>

=== Chemical ===
Chemical eye injury may result when an [[acidic]] or [[alkali]]ne substance gets in the eye.<ref name="Bet09">{{cite journal | vauthors = Zentani A, Burslem J | title = Towards evidence based emergency medicine: best BETs from the Manchester Royal Infirmary. BET 4: use of litmus paper in chemical eye injury | journal = Emergency Medicine Journal | volume = 26 | issue = 12 | pages = 887 | date = December 2009 | pmid = 19934140 | doi = 10.1136/emj.2009.086124 | s2cid = 38124735 }}</ref> Alkali burns are typically worse than acidic burns.<ref name=AFP08/> Mild burns produce conjunctivitis, while more severe burns may cause the [[cornea]] to turn white.<ref name=AFP08/> [[Litmus|Litmus paper]] may be used to test for chemical causes.<ref name=Bet09/> When a chemical cause has been confirmed, the eye or eyes should be flushed until the [[pH]] is in the range 6–8.<ref name="AFP08">{{cite journal | vauthors = Hodge C, Lawless M | title = Ocular emergencies | journal = Australian Family Physician | volume = 37 | issue = 7 | pages = 506–509 | date = July 2008 | pmid = 18592066 }}</ref> Anaesthetic eye drops can be used to decrease the pain.<ref name=AFP08/>

Irritant or toxic conjunctivitis is primarily marked by redness. If due to a chemical splash, it is often present in only the lower conjunctival sac.  With some chemicals, above all with caustic alkalis such as [[sodium hydroxide]], [[necrosis]] of the conjunctiva marked by a deceptively white eye due to vascular closure may occur, followed by sloughing off of the dead [[epithelium]]. A slit lamp examination is likely to show evidence of [[iritis|anterior uveitis]].<ref>{{Cite web |title=Diagnosing Conjunctivitis |url=https://nyulangone.org/conditions/conjunctivitis/diagnosis |access-date=2025-02-13 |website=nyulangone.org |language=en}}</ref>

=== Biomarkers ===
Omics technologies have been used to identify biomarkers that inform on the emergence and progression of conjunctivitis. For example, in chronic inflammatory cicatrizing conjunctivitis, active [[oxylipins]], [[lysophospholipid]]s, [[fatty acid]]s, and [[endocannabinoid]]s alterations, from which potential biomarkers linked to inflammatory processes were identified.<ref>{{cite journal | vauthors = Di Zazzo A, Yang W, Coassin M, Micera A, Antonini M, Piccinni F, De Piano M, Kohler I, Harms AC, Hankemeier T, Boinini S, Mashaghi A | title = Signaling lipids as diagnostic biomarkers for ocular surface cicatrizing conjunctivitis | journal = Journal of Molecular Medicine | volume = 98 | issue = 5 | pages = 751–760 | date = May 2020 | pmid = 32313985 | pmc = 7220886 | doi = 10.1007/s00109-020-01907-w }}</ref>

=== Other ===

[[File:Chlamydial-conjunctivitis.jpg|thumb|right|An eye with chlamydial conjunctivitis]]
Inclusion conjunctivitis of the newborn is a conjunctivitis that may be caused by the bacterium ''Chlamydia trachomatis'', and may lead to acute, [[purulent]] conjunctivitis.<ref name="Microbiology">{{Cite book | vauthors =  Fisher B, Harvey RP, Champe PC |title=Lippincott's Illustrated Reviews: Microbiology (Lippincott's Illustrated Reviews Series) |publisher=Lippincott Williams & Wilkins |year=2007 |isbn=978-0-7817-8215-9 |location=Hagerstown MD}}</ref> However, it is usually self-healing.<ref name=Microbiology/>

== Causes ==
Infective conjunctivitis is most commonly caused by a virus.<ref name=Az2013/> Bacterial infections, allergies, other irritants, and dryness are also common causes. Both bacterial and viral infections are contagious, passing from person to person or spread through contaminated objects or water. Contact with contaminated fingers is a common cause of conjunctivitis. Bacteria may also reach the conjunctiva from the edges of the eyelids and the surrounding skin, from the nasopharynx, from infected eye drops or contact lenses, from the genitals or the bloodstream.<ref name=":1" /> Infection by human adenovirus accounts for 65% to 90% of cases of viral conjunctivitis.<ref>{{cite journal | vauthors = Singh MP, Ram J, Kumar A, Rungta T, Gupta A, Khurana J, Ratho RK | title = Molecular epidemiology of circulating human adenovirus types in acute conjunctivitis cases in Chandigarh, North India | journal = Indian Journal of Medical Microbiology | volume = 36 | issue = 1 | pages = 113–115 | date = 2018 | pmid = 29735838 | doi = 10.4103/ijmm.ijmm_17_258 | doi-access = free }}</ref>

=== Viral ===
[[Adenoviruses]] are the most common cause of viral conjunctivitis ([[adenoviral keratoconjunctivitis]]).<ref name=Yanoff/> [[Herpetic keratoconjunctivitis]], caused by [[herpes simplex]] viruses, can be serious and requires treatment with [[aciclovir]]. Acute hemorrhagic conjunctivitis is a highly contagious disease caused by one of two [[enterovirus]]es, enterovirus 70 and [[coxsackievirus]] A24. These were first identified in an outbreak in Ghana in 1969, and have spread worldwide since then, causing several epidemics.<ref>{{cite journal | vauthors = Lévêque N, Huguet P, Norder H, Chomel JJ | title = [Enteroviruses responsible for acute hemorrhagic conjunctivitis] | language = fr | journal = Médecine et Maladies Infectieuses | volume = 40 | issue = 4 | pages = 212–218 | date = April 2010 | pmid = 19836177 | doi = 10.1016/j.medmal.2009.09.006 }}</ref>

=== Bacterial ===
The most common causes of acute bacterial conjunctivitis are ''[[Staphylococcus aureus]]'', ''[[Streptococcus pneumoniae]]'', and ''[[Haemophilus influenzae]]''.<ref name="Yanoff">{{Cite book | vauthors = Yanoff M, Duker JS |title=Ophthalmology |publisher=Mosby |year=2008 |isbn=978-0-323-05751-6 |edition=3rd |location=Edinburgh |pages=227–236}}</ref><ref>{{Cite web |date=2017-10-02 |title=Protect Yourself From Pink Eye |url=https://www.cdc.gov/conjunctivitis/about/causes.html |access-date=2018-12-07 |website=Centers for Disease Control and Prevention (CDC) |language=en-us}}</ref> Though very rare, hyperacute cases are usually caused by ''[[Neisseria gonorrhoeae]]'' or ''[[Neisseria meningitidis]]''.  Chronic cases of bacterial conjunctivitis are those lasting longer than 3 weeks, and are typically caused by ''S. aureus'', ''[[Morax-Axenfeld diplobacilli|Moraxella lacunata]]'', or Gram-negative enteric flora.{{citation needed|date=September 2022}}

=== Allergic ===
Conjunctivitis may also be caused by allergens such as pollen, perfumes, cosmetics, smoke,<ref name="FD">{{Cite web |title=Allergic Conjunctivitis |url=http://familydoctor.org/familydoctor/en/diseases-conditions/allergic-conjunctivitis/causes-risk-factors.html |url-status=live |archive-url=https://web.archive.org/web/20150906031026/http://familydoctor.org/familydoctor/en/diseases-conditions/allergic-conjunctivitis/causes-risk-factors.html |archive-date=6 September 2015 |access-date=18 September 2015 |publisher=familydoctor.org |df=dmy-all}}</ref>{{Unreliable medical source|date=September 2015}} dust mites, [[Balsam of Peru]],<ref name="google1">{{Cite book | vauthors = Brooks P |url=https://books.google.com/books?id=eReGG6UtxbcC&pg=PT413 |title=The Daily Telegraph: Complete Guide to Allergies |date=25 October 2012 |publisher=Little, Brown Book |isbn=978-1-4721-0394-9 |access-date=15 April 2014}}{{Dead link|date=September 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> or eye drops.<ref name="MedNews">{{Cite web |title=What Is Allergic Conjunctivitis? What Causes Allergic Conjunctivitis? |url=http://www.medicalnewstoday.com/articles/157692.php |url-status=live |archive-url=https://web.archive.org/web/20100316174827/http://www.medicalnewstoday.com/articles/157692.php |archive-date=16 March 2010 |access-date=6 April 2010 |publisher=medicalnewstoday.com |df=dmy-all}}</ref> The most frequent cause of conjunctivitis is allergic conjunctivitis and it affects 15% to 40% of the population.<ref name=":0" /> Allergic conjunctivitis accounts for 15% of eye related primary care consultations; most including seasonal exposures in the spring and summer or perpetual conditions.<ref>{{cite journal | vauthors = Perkin MR, Bader T, Rudnicka AR, Strachan DP, Owen CG | title = Inter-Relationship between Rhinitis and Conjunctivitis in Allergic Rhinoconjunctivitis and Associated Risk Factors in Rural UK Children | journal = PLOS ONE | volume = 10 | issue = 11 | pages = e0143651 | date = 2015-11-24 | pmid = 26600465 | pmc = 4658044 | doi = 10.1371/journal.pone.0143651 | bibcode = 2015PLoSO..1043651P | doi-access = free }}</ref>

=== Other ===
* [[Computer vision syndrome]]
* [[Dry eye syndrome]]
* [[Reactive arthritis]]: Conjunctivitis is part of the triad of [[reactive arthritis]], which is thought to be caused by [[autoimmune]] cross-reactivity following certain bacterial infections. Reactive arthritis is highly associated with [[HLA-B27]]. Conjunctivitis is associated with the autoimmune disease [[relapsing polychondritis]].<ref name="Puechal 2014">{{cite journal | vauthors = Puéchal X, Terrier B, Mouthon L, Costedoat-Chalumeau N, Guillevin L, Le Jeunne C | title = Relapsing polychondritis | journal = Joint Bone Spine | volume = 81 | issue = 2 | pages = 118–124 | date = March 2014 | pmid = 24556284 | doi = 10.1016/j.jbspin.2014.01.001 | s2cid = 205754989 }}</ref><ref name="Cantarini 2014">{{cite journal | vauthors = Cantarini L, Vitale A, Brizi MG, Caso F, Frediani B, Punzi L, Galeazzi M, Rigante D | title = Diagnosis and classification of relapsing polychondritis | journal = Journal of Autoimmunity | volume = 48-49 | pages = 53–59 | year = 2014 | pmid = 24461536 | doi = 10.1016/j.jaut.2014.01.026 }}</ref>

== Diagnosis ==
[[File:Procedure of conjunctival swabs.jpg|thumb|The procedure of conjunctival swabs]]

Cultures are not often taken or needed as most cases resolve either with time or typical antibiotics. If bacterial conjunctivitis is suspected, but no response to topical antibiotics is seen, swabs for bacterial culture should be taken and tested. Viral culture may be appropriate in epidemic case clusters.<ref>{{cite book | vauthors = Sheikh A, Hurwitz B | chapter = BACTERIAL CONJUNCTIVITIS 372.05 (Infective Conjunctivitis, Mucopurulent Conjunctivitis, Purulent Conjunctivitis) |date=2008 | title = Roy and Fraunfelder's Current Ocular Therapy |pages=332–334 |publisher=Elsevier |doi=10.1016/b978-1-4160-2447-7.50182-1 |isbn=978-1-4160-2447-7 }}</ref>

A [[patch test]] is used to identify the causative allergen in allergic conjunctivitis.<ref name="google2">{{Cite book | vauthors = Mannis MJ, Macsai MS, Huntley AC |url=https://books.google.com/books?id=FtlsAAAAMAAJ&q=Conjunctivitis+%22patch+test%22 |title=Eye and skin disease |date=1996 |publisher=Lippincott-Raven |isbn=978-0-7817-0269-0 |access-date=23 April 2014 |archive-url=https://web.archive.org/web/20140705035958/http://books.google.com/books?id=FtlsAAAAMAAJ&q=Conjunctivitis+%22patch+test%22&dq=Conjunctivitis+%22patch+test%22&hl=en&sa=X&ei=oY9UU932MMPjsAT5j4KYCg&ved=0CF8Q6AEwBg |archive-date=5 July 2014 |url-status=live |df=dmy-all}}</ref>

Although conjunctival scrapes for [[Cytopathology|cytology]] can be useful in detecting chlamydial and [[Fungus#Mycology|fungal]] infections, allergies, and [[dysplasia]], they are rarely done because of the cost and the general dearth of laboratory staff experienced in handling ocular specimens. Conjunctival incisional biopsy is occasionally done when [[granulomatous]] diseases (''e.g.'', [[sarcoidosis]])<ref>{{cite journal | vauthors = Korkmaz Ekren P, Mogulkoc N, Toreyin ZN, Egrilmez S, Veral A, Akalın T, Bacakoglu F | title = Conjunctival Biopsy as a First Choice to Confirm a Diagnosis of Sarcoidosis | journal = Sarcoidosis, Vasculitis, and Diffuse Lung Diseases | volume = 33 | issue = 3 | pages = 196–200 | date = October 2016 | pmid = 27758983 | url = https://pubmed.ncbi.nlm.nih.gov/27758983/ }}</ref> or dysplasia are suspected.<ref>{{cite book | vauthors = Roberts F, Thum CK | chapter = The Conjunctival Biopsy |date=2021 | title = Lee's Ophthalmic Histopathology |pages=343–388 | veditors = Roberts F |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-76525-5_11 |isbn=978-3-030-76525-5 }}</ref>

=== Classification ===
Conjunctivitis may be classified either by cause or by extent of the inflamed area.{{citation needed|date=February 2023}}

==== Causes ====
* Allergy
* Bacteria
* Viruses
* Chemicals
* Autoimmune

Neonatal conjunctivitis is often grouped separately from bacterial conjunctivitis because it is caused by different bacteria than the more common cases of bacterial conjunctivitis.{{citation needed|date=February 2023}}<!-- Source? -->

==== By extent of involvement ====
Blepharoconjunctivitis is the dual combination of conjunctivitis with [[blepharitis]] (inflammation of the eyelids).{{citation needed|date=February 2023}}

[[Keratoconjunctivitis]] is the combination of conjunctivitis and [[keratitis]] ([[cornea]]l inflammation).{{citation needed|date=February 2023}}<!-- Two good bullet points, but try to find a source for them. -->

Blepharokeratoconjunctivitis is the combination of conjunctivitis with blepharitis and keratitis. It is clinically defined by changes of the lid margin, meibomian gland dysfunction, redness of the eye, conjunctival chemosis and inflammation of the cornea.<ref name="OGallagher">{{cite journal | vauthors = O'Gallagher M, Banteka M, Bunce C, Larkin F, Tuft S, Dahlmann-Noor A | title = Systemic treatment for blepharokeratoconjunctivitis in children | journal = The Cochrane Database of Systematic Reviews | volume = 2016 | issue = 5 | pages = CD011750 | date = May 2016 | pmid = 27236587 | pmc = 9257284 | doi = 10.1002/14651858.CD011750.pub2 }}</ref>

=== Differential diagnosis ===

Some more serious conditions can present with a red eye, such as infectious keratitis, angle-closure glaucoma, or iritis. These conditions require the urgent attention of an ophthalmologist. Signs of such conditions include decreased vision, significantly increased sensitivity to light, inability to keep the eye open, a pupil that does not respond to light, or a severe headache with nausea.<ref name="McGra-Hill">{{Cite book |title=Harrison's Principles of Internal Medicine |vauthors=Longo DL |date=2012 |publisher=McGra-Hill |chapter=Disorders of the Eye(Horton JC)}}</ref> Fluctuating blurring is common, due to tearing and mucoid discharge.  Mild photophobia is common. However, if any of these symptoms is prominent, considering other diseases such as [[glaucoma]], [[uveitis]], [[keratitis]], and even [[meningitis]] or [[caroticocavernous fistula|carotico-cavernous fistula]] is important.{{citation needed|date=September 2022}}

A more comprehensive differential diagnosis for the red or painful eye includes:<ref name="McGra-Hill" />
* [[Corneal abrasion]]
* [[Subconjunctival hemorrhage]]
* [[Pinguecula]]
* [[Blepharitis]]
* [[Dacryocystitis]]
* [[Keratoconjunctivitis sicca]] (dry eye)
* [[Keratitis]]
* [[Herpes simplex]]
* [[Herpes zoster]]
* [[Episcleritis]] – an [[Inflammation|inflammatory]] condition that produces a similar appearance to conjunctivitis, but without discharge or tearing
* [[Uveitis]]
* [[Acute angle-closure glaucoma]]
* [[Endophthalmitis]]
* [[Orbital cellulitis]]

== Prevention ==
The most effective prevention is good hygiene, especially avoiding rubbing the eyes with infected hands. Vaccination against some of the causative pathogens such as ''Haemophilus influenzae'', pneumococcus, and ''Neisseria meningitidis'' is also effective.<ref>{{Cite news |date=2 October 2017 |title=Protect Yourself From Pink Eye |url=https://www.cdc.gov/conjunctivitis/about/prevention.html |access-date=18 October 2017 |work=Centers for Disease Control and Prevention |language=en-us}}</ref>

[[Povidone-iodine]] eye solution has been found to prevent neonatal conjunctivitis.<ref name=Is2003/> It is becoming more commonly used globally because of its low cost.<ref name="Is2003">{{cite journal | vauthors = Isenberg SJ | title = The ocular application of povidone-iodine | journal = Community Eye Health | volume = 16 | issue = 46 | pages = 30–31 | date = 2003 | pmid = 17491857 | pmc = 1705857 }}</ref>

== Management ==
Conjunctivitis resolves in 65% of cases without treatment, within 2–5 days. The prescription of antibiotics is not necessary in most cases.<ref>{{cite journal | vauthors = Rose P | title = Management strategies for acute infective conjunctivitis in primary care: a systematic review | journal = Expert Opinion on Pharmacotherapy | volume = 8 | issue = 12 | pages = 1903–1921 | date = August 2007 | pmid = 17696792 | doi = 10.1517/14656566.8.12.1903 | s2cid = 45899988 }}</ref>

=== Viral ===
Viral conjunctivitis usually resolves on its own and does not require any specific treatment.<ref name=Az2013/> Antihistamines (e.g., [[diphenhydramine]]) or mast cell stabilizers (e.g., [[Cromoglicic acid|cromolyn]]) may be used to help with the symptoms.<ref name=Az2013/> Povidone-iodine has been suggested as a treatment, but as of 2008, evidence to support it was poor.<ref name="BartlettJaanus2008">{{Cite book | vauthors = Bartlett JD, Jaanus SD |url=https://books.google.com/books?id=Eybg7fbs65MC&pg=PA454 |title=Clinical Ocular Pharmacology |publisher=Elsevier Health Sciences |year=2008 |isbn=978-0-7506-7576-5 |pages=454– |archive-url=https://web.archive.org/web/20161203204429/https://books.google.com/books?id=Eybg7fbs65MC&pg=PA454 |archive-date=3 December 2016 |url-status=live |df=dmy-all}}</ref>

=== Allergic ===
For allergic conjunctivitis, cool water poured over the face with the head inclined downward constricts capillaries, and [[artificial tears]] sometimes relieve discomfort in mild cases. In more severe cases, [[NSAID|nonsteroidal anti-inflammatory medications]] and [[antihistamine]]s may be prescribed. Persistent allergic conjunctivitis may also require topical steroid drops.<ref>{{cite journal | vauthors = Patel DS, Arunakirinathan M, Stuart A, Angunawela R | title = Allergic eye disease | journal = BMJ | volume = 359 | pages = j4706 | date = November 2017 | pmid = 29097360 | doi = 10.1136/bmj.j4706 | s2cid = 5316455 }}</ref>

=== Bacterial ===
Bacterial conjunctivitis usually resolves without treatment.<ref name=Az2013/> Topical antibiotics may be needed only if no improvement is observed after 3 days.<ref>{{cite journal | vauthors = Visscher KL, Hutnik CM, Thomas M | title = Evidence-based treatment of acute infective conjunctivitis: Breaking the cycle of antibiotic prescribing | journal = Canadian Family Physician | volume = 55 | issue = 11 | pages = 1071–1075 | date = November 2009 | pmid = 19910590 | pmc = 2776793 }}</ref> No serious effects were noted either with or without treatment.<ref name=":2">{{cite journal | vauthors = Chen YY, Liu SH, Nurmatov U, van Schayck OC, Kuo IC | title = Antibiotics versus placebo for acute bacterial conjunctivitis | journal = The Cochrane Database of Systematic Reviews | volume = 3 | issue = 3 | pages = CD001211 | date = March 2023 | pmid = 36912752 | pmc = 10014114 | doi = 10.1002/14651858.CD001211.pub4 }}</ref> Because antibiotics do speed healing in bacterial conjunctivitis, their use may be considered.<ref name=":2" /> Antibiotics are also recommended for those who wear contact lenses, are [[immunocompromised]], have disease which is thought to be due to chlamydia or gonorrhea, have a fair bit of pain, or have copious discharge.<ref name=Az2013/> Gonorrheal or chlamydial infections require both oral and topical antibiotics.<ref name=Az2013/>

The choice of antibiotic varies based on the strain or suspected strain of bacteria causing the infection. [[Fluoroquinolones]], [[sodium sulfacetamide]], or [[trimethoprim/polymyxin]] may be used, typically for 7–10 days.<ref name="Yanoff" />  Cases of meningococcal conjunctivitis can also be treated with systemic penicillin, as long as the strain is sensitive to penicillin.{{citation needed|date=September 2022}}

When investigated as a treatment, povidone-iodine ophthalmic solution has also been observed to have some effectiveness against bacterial and chlamydial conjunctivitis, with a possible role suggested in locations where topical antibiotics are unavailable or costly.<ref name="Am J Ophthalmol 2002">{{cite journal | vauthors = Isenberg SJ, Apt L, Valenton M, Del Signore M, Cubillan L, Labrador MA, Chan P, Berman NG | title = A controlled trial of povidone-iodine to treat infectious conjunctivitis in children | journal = American Journal of Ophthalmology | volume = 134 | issue = 5 | pages = 681–688 | date = November 2002 | pmid = 12429243 | doi = 10.1016/S0002-9394(02)01701-4 }}</ref>

=== Chemical ===
Conjunctivitis due to chemicals is treated via [[Therapeutic irrigation|irrigation]] with [[Ringer's lactate]] or [[saline (medicine)|saline solution]]. Chemical injuries, particularly alkali burns, are medical emergencies, as they can lead to severe scarring and intraocular damage. People with chemically induced conjunctivitis should not touch their eyes to avoid spreading the chemical.<ref>{{Cite web |title=Conjunctivitis |url=https://www.aoa.org/healthy-eyes/eye-and-vision-conditions/conjunctivitis?sso=y |access-date=March 15, 2024 |website=American Optometric Association}}</ref>

== Epidemiology ==
Conjunctivitis is the most common eye disease.<ref>{{Cite book | vauthors = Smeltzer SC |url=https://books.google.com/books?id=SmtjSD1x688C&pg=RA1-PA1787 |title=Brunner & Suddarth's textbook of medical-surgical nursing. |date=2010 |publisher=Wolters Kluwer Health/Lippincott Williams & Wilkins |isbn=978-0-7817-8589-1 |edition=12th |location=Philadelphia |page=1787 |archive-url=https://web.archive.org/web/20160815203433/https://books.google.ca/books?id=SmtjSD1x688C&pg=RA1-PA1787 |archive-date=15 August 2016 |url-status=live |df=dmy-all}}</ref> Rates of disease is related to the underlying cause which varies by the age as well as the time of year. Acute conjunctivitis is most frequently found in infants, school-age children and the elderly.<ref name=":1">{{cite journal | vauthors = Høvding G | title = Acute bacterial conjunctivitis | journal = Acta Ophthalmologica | volume = 86 | issue = 1 | pages = 5–17 | date = February 2008 | pmid = 17970823 | doi = 10.1111/j.1600-0420.2007.01006.x | s2cid = 20629824 | doi-access = free }}</ref> The most common cause of infectious conjunctivitis is viral conjunctivitis.<ref name=":0">{{Cite journal | vauthors = Mourad MS, Rihan RA |date=April 2018 |title=Prevalence of Different Eye Diseases excluding Refractive Errors Presented at the Outpatient Clinic in Beheira Eye Hospital |journal=The Egyptian Journal of Hospital Medicine |language=en |volume=71 |issue=2 |pages=2484–2489 |doi=10.12816/0045645 |s2cid=80882721}}</ref>

It is estimated that acute conjunctivitis affects 6 million people annually in the United States.<ref name=Az2013/>

Some seasonal trends have been observed for the occurrence of different forms of conjunctivitis. In the northern hemisphere, the occurrence of bacterial conjunctivitis peaks from December to April, viral conjunctivitis peaks in the summer months and allergic conjunctivitis is more prevalent throughout the spring and summer.<ref name=":1" /><!-- Include more on epidemiology if more info can be found. -->

== History ==
An adenovirus was first isolated by Rowe et al. in 1953. Two years later, Jawetz et al. published on epidemic keratoconjunctivitis.<ref>{{cite journal | vauthors = Jhanji V, Chan TC, Li EY, Agarwal K, Vajpayee RB | title = Adenoviral keratoconjunctivitis | journal = Survey of Ophthalmology | volume = 60 | issue = 5 | pages = 435–443 | date = September–October 2015 | pmid = 26077630 | doi = 10.1016/j.survophthal.2015.04.001 }}</ref>{{rp|437}} "Madras eye" is a colloquial term that has been used in [[India]] for the disease.<!-- Try to elaborate on the history a bit more. -->

===Outbreak in Pakistan===
{{Main|Pink eye outbreak in Pakistan}}

In September 2023, a significant outbreak of conjunctivitis occurred in [[Pakistan]]. The outbreak began in [[Karachi]] and quickly spread to [[Lahore]], [[Rawalpindi]], and [[Islamabad]]. By the end of the month, over 86,133 cases had been reported in [[Punjab, Pakistan|Punjab]] alone. The rapid spread of the disease led to the temporary closure of schools in the region. This event marked one of the largest outbreaks of Pink Eye in the country's recent history.<ref>{{Cite web |date=28 September 2023 |title=From pink eye to blindness |url=https://tribune.com.pk/story/2438104/from-pink-eye-to-blindness}}</ref><ref>{{Cite web |date=28 September 2023 |title=86,133 pink eye cases in Punjab in September and counting |url=https://www.dawn.com/news/1778214}}</ref><ref>{{Cite news |last=Ahmed |first=Salman |date=27 September 2023 |title=Punjab Announces Holiday for Schools Amid Pink Eye Outbreak |url=https://propakistani.pk/2023/09/27/punjab-announces-holiday-for-schools-amid-pink-eye-outbreak/ |work=Propakistani}}</ref><ref>{{Cite web |title=85 new cases of Pink Eye infection reported in Pakistan's Lahore |url=https://health.economictimes.indiatimes.com/news/industry/85-new-cases-of-pink-eye-infection-reported-in-pakistans-lahore/103921170 |website=ETHealthworld.com |agency=[[Asian News International]]}}</ref>

==Society and culture==
Conjunctivitis imposes economic and social burdens. The cost of treating bacterial conjunctivitis in the United States was estimated to be $377 million to $857 million per year.<ref name=Az2013/> Approximately 1% of all primary care office visits in the United States are related to conjunctivitis. Approximately 70% of all people with acute conjunctivitis present to primary care and urgent care.<ref name=Az2013/>

== See also ==
* [[Conjunctival suffusion]]
* [[Ophthalmia]]

== References ==
{{Reflist}}

== External links ==
{{commons category|Conjunctivitis}}
* 
* {{Cite web |title=Pink Eye |url=https://medlineplus.gov/pinkeye.html |website=MedlinePlus |publisher=U.S. National Library of Medicine}}
* {{Cite web |date=28 February 2021 |title=Metabolomics for Ocular Surface Disease |url=https://www.youtube.com/watch?v=PuG1hvcdZBQ |publisher=MSBB Group, Leiden University}}

{{Medical condition classification and resources
 |ICD10          = {{ICD10|H|10||h|10}}
 |ICD9           = {{ICD9|372.0}}
 |OMIM           =
 |MedlinePlus    = 001010
 |eMedicineSubj  = emerg
 |eMedicineTopic = 110
 |DiseasesDB     = 3067
 |MeshID         = D003231 |
}}
{{Eye pathology}}
{{Authority control}}

[[Category:Eye diseases]]
[[Category:Disorders of conjunctiva]]
[[Category:Inflammations]]
[[Category:Measles]]
[[Category:Wikipedia medicine articles ready to translate]]
[[Category:Wikipedia emergency medicine articles ready to translate]]